Generally, there are two ways to perform a transaction in an ETC system. The first way is implemented with a stop bar, that is, vehicles enter into one lane with the stop bar one after another and a road side unit (RSU) of the lane communicates with one vehicle in this lane each time. The second way is called free flow and there is no stop bar in the lane. In this way, vehicles can pass through any lane and the RSU communicates with vehicles in different lanes in the same time period by utilizing multiple time windows to communicate with the on-board units (OBU) of vehicles. Wherein the shortest time window is 192 us, and if the communication cannot be completed within 192 us, the transaction may fail.
To shorten the communication time and complete the transaction, an OBU and a method for improving the performance of transmitting and receiving may be necessary.